US4616194A - Piezoelectric oscillator with crystal filter and temperature compensation - Google Patents

Piezoelectric oscillator with crystal filter and temperature compensation Download PDF

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US4616194A
US4616194A US06/715,822 US71582285A US4616194A US 4616194 A US4616194 A US 4616194A US 71582285 A US71582285 A US 71582285A US 4616194 A US4616194 A US 4616194A
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resonator
mode
oscillator
transistor
frequency
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US06/715,822
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Patrick Renoult
Gerard Marotel
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D'ELECTRONIQUE ET DE PIEZO-ELECTRCITE CEPE Cie
Compagnie Electronique et de Piezoelectricite CEPE
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Compagnie Electronique et de Piezoelectricite CEPE
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L1/00—Stabilisation of generator output against variations of physical values, e.g. power supply
    • H03L1/02—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only
    • H03L1/022—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature
    • H03L1/023—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature by using voltage variable capacitance diodes
    • H03L1/025—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature by using voltage variable capacitance diodes and a memory for digitally storing correction values
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/30—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator
    • H03B5/32—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator
    • H03B5/36—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator active element in amplifier being semiconductor device
    • H03B5/362—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator active element in amplifier being semiconductor device the amplifier being a single transistor

Definitions

  • the present invention relates to a piezoelectric oscillator operating in the aperiodic mode, of the CLAPP type.
  • a piezoelectric oscillator operating in the aperiodic or overtone mode is known, of the CLAPP type.
  • This oscillator comprises a piezoelectric resonator having a resonance frequency at which the oscillator is to operate, with a first resonator being connected between the base of a transistor and ground, and a capacitive divider bridge having a so called middle point.
  • the emitter of the transistor is loaded by way of a load resistor.
  • the object of the invention is to provide an oscillator of the above type having better selectivity provided by narrow band-pass filtering.
  • the second piezoelectric resonator having in common with the first resonator a mode at said resonance frequency, but whose intrinsic quality factor is between 30 and a 1000 times smaller, the second resonator being connected between the middle point of the capacitive divider bridge and the emitter of the transistor.
  • the second resonator is chosen so that the mode at said resonance frequency is the only mode common to the first and second resonators.
  • the intrinsic quality factor of the second resonator is advantageously of the order of 30 to a 100 times less than that of the first resonator and preferably of the order of a 100 times less.
  • this variant is more particularly suitable in the case where the first resonator is used in one of these partial modes. It will in fact be recalled that the two modes of the same partial are separated by a relative frequency difference of the order of 10%.
  • the oscillator comprises a third piezoelectric resonator having in common with the first resonator a mode at said resonance frequency, whose quality factor is of the same order of size as that of the second resonator, said third resonator being connected in series between the ungrounded terminal of the first resonator and the base of the transistor.
  • the oscillator is advantageously associated with a temperature detector and a servocontrol of the temperature of the first resonator.
  • the oscillator comprises a Varicap diode connected in series with said third resonator so as to form a frequency control for the oscillator, it comprises a temperature detector and a compensation circuit producing a control voltage on the Varicap diode so that the frequency drift of the oscillator is compensated for.
  • the first resonator may advantageously have, at said resonance frequency, a stable frequency mode depending on the temperature as well as a so called thermometric mode whose frequency varies with the temperature, the temperature detector then being formed by an oscillator operating in the thermometric mode of the first resonator and whose frequency varies therefore with the temperature thereof.
  • the first resonator can for example be an SC cut quartz, the stable frequency mode being a C mode, and the thermometric mode a B mode.
  • the C mode and the B mode may both belong to the fundamental F or both to a partial of the same rank.
  • the temperature sensitive oscillator employs a second transistor.
  • a fourth piezoelectric resonator is connected between the ungrounded end of the first resonator and the base of the second transistor.
  • a capacitive divider bridge having a so called middle point is connected between the base of the second transistor and ground, with the emitter of the second transistor being loaded by a second load resistor.
  • a fifth piezoelectric resonator connects the second middle point to the emitter of the second transistor.
  • the fourth and fifth resonators having in common a mode at the frequency of said thermometric mode of the first resonator, with a quality factor between 30 and a 1000 times smaller than the latter.
  • the collector of the second transistor thereby produces a frequency voltage which varies substantially linearly with the temperature of the first resonator.
  • FIG. 1 one embodiment of an oscillator according to the invention
  • FIG. 2 an embodiment of a temperature compensated oscillator according to the invention.
  • FIG. 3 curves representative of the temperature frequency drift in the case of an SC cut quartz.
  • a transistor T 1 is supplied with the voltage +V at its collector C 1 , a divider bridge R 1 ,R 2 biasing its base B 1 .
  • the emitter E 1 is loaded by a load resistor R 3 .
  • the piezoelectric resonator Q 1 is connected between the base B 1 of transistor T 1 and ground.
  • a capacitive divider bridge C 1 ,C 2 having a so called middle point P 1 is also connected between the base B 1 of transistor T 1 and ground.
  • a piezoelectric resonator Q 2 is connected between the middle point P 1 and the emitter E 1 of transistor T 1 .
  • the function of this resonator Q 2 is to form a band-pass filter at the operating frequency of the oscillator.
  • resonator Q 2 must have a mode at the same frequency as the mode of resonator Q 1 chosen for determining a frequency of the oscillator.
  • the band-pass filter is formed by choosing resonator Q 2 with a quality factor which is 30 to 1000 times smaller than that of resonator Q 1 .
  • the oscillator will start up at the chosen frequency without being troubled by thermodrifting.
  • It is very easy to provide a resonator with a quality factor smaller than that of resonator Q 1 since several parameters influence the quality factor of the resonator.
  • Such parameters comprise for example the quality of the cut and the thickness and arrangement of the electrodes.
  • an oscillator such as shown in FIG. 1, is associated with a second oscillator having a high thermal drift.
  • an SC cut quartz has for its partial 3 a C mode whose frequency drift curve as a function of the temperature has a small slope close to a temperature ⁇ ° and a practically linear B mode over a large temperature range with high thermal drift.
  • the C mode of the partial 3 of quartz Q 1 is used as temperature stable frequency reference and the slight thermal drift of this C mode is compensated for by using the B mode of the same quartz as temperature sensor.
  • This design has the very important advantage of using, as temperature sensor, the quartz itself whose frequency it is desired to stabilize. It is then certain that the temperature measured is exactly that which is desired.
  • This oscillator has however in addition a frequency control circuit comprising a low value Varicap diode C R connected between two capacitors C 5 and C 6 in series with the base of transistor T 1 .
  • a biasing resistor R 5 biases the cathode of the varicap diode C R and a control voltage V C is applied to the anode of the varicap diode C R through a coupling resistor R 6 .
  • Such a frequency control circuit for slightly varying the frequency of the oscillator is moreover known per se.
  • a piezoelectric resonator Q 3 having a mode at the frequency of the C mode of resonator Q 1 corresponding to the desired frequency of the oscillator, with a quality factor of the order of 30 to 1000 times smaller and preferably 30 to 100 times smaller.
  • Resonator Q.sub. 3 improves the separation between the C modes at which the main oscillator operates and the B mode at which the oscillator used as thermal sensor operates.
  • the thermal sensor oscillator has a CLAPP circuit similar to that of the oscillator of FIG. 1.
  • the collector of a transistor T 2 is biased by a voltage B through a biasing resistor R 9 and its base by a divider bridge R 8 , R 4 .
  • a capacitive divider bridge C 3 , C 4 having a so called middle point P 2 is connected between the base B 2 of transistor T 2 and ground.
  • the emitter E2 of transistor T 2 is loaded by a load resistor R 10 .
  • the piezoelectric resonator is connected between the emitter E2 and the middle point P 2 . It has a mode whose frequency is that of the B mode close to the C mode at which the main oscillator operates.
  • Resonators Q 4 and Q 5 have a quality factor 30 to 1000 times smaller and preferably a 100 times smaller than that of the B mode considered for resonator Q 1 .
  • the output voltage S T present at the collector C 2 of transistor T 2 is fed to a frequency-voltage converter 1 which outputs a digitalized voltage which is fed into a memory 2.
  • Each value of the output voltage of converter 1 corresponds to an address in memory 2, at which address a stored voltage is read at a rate determined by a sampling clock H.
  • This stored voltage is the reflection of the correspondance between the thermal drift curves in the B mode and the C mode of the quartz Q 1 and its value corresponds to that of the voltage V C which must be fed into the frequency variation circuit of the main oscillator for providing the thermal drift correction.
  • each value read in the memory at the rate of the sampling clock is fed to a digital-analog converter 3 whose output voltage V C is applied to the resistor R 6 .

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  • Oscillators With Electromechanical Resonators (AREA)

Abstract

A piezoelectric oscillator operating in the aperiodic or overtone mode comprising a first piezoelectric resonator having a resonance frequency at which the oscillator is to operate. One side of the first resonator is connected to ground, and the other side is connected through a second piezoelectric resonator to the base of a transistor. The second resonator has in common with the first resonator a mode at the resonance frequency, but its intrinsic quality factor is between 30 and 1000 times smaller than that of the first resonator. A capacitive divider bridge having a middle point is connected between the base of the transistor and ground. A third piezoelectric resonator having in common with said first resonator a mode at said resonance frequency, but whose intrinsic quality factor is of the same order of size as that of the second resonator, is connected between said middle point and the emitter of said transistor. A temperature sensing circuit is coupled to the oscillator and provides a control signal to a Varicap diode connected in the base circuit of the transistor, to compensate for frequency drift due to changes in temperature.

Description

BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric oscillator operating in the aperiodic mode, of the CLAPP type.
From the U.S. Pat. No. 4,484,157 belonging to the applicant a piezoelectric oscillator operating in the aperiodic or overtone mode is known, of the CLAPP type. This oscillator comprises a piezoelectric resonator having a resonance frequency at which the oscillator is to operate, with a first resonator being connected between the base of a transistor and ground, and a capacitive divider bridge having a so called middle point. The emitter of the transistor is loaded by way of a load resistor.
SUMMARY OF THE INVENTION
The object of the invention is to provide an oscillator of the above type having better selectivity provided by narrow band-pass filtering.
For this, it comprises a second piezoelectric resonator having in common with the first resonator a mode at said resonance frequency, but whose intrinsic quality factor is between 30 and a 1000 times smaller, the second resonator being connected between the middle point of the capacitive divider bridge and the emitter of the transistor.
In an advantageous variant, the second resonator is chosen so that the mode at said resonance frequency is the only mode common to the first and second resonators.
The intrinsic quality factor of the second resonator is advantageously of the order of 30 to a 100 times less than that of the first resonator and preferably of the order of a 100 times less.
Because of the high selectivity which is obtained, this variant is more particularly suitable in the case where the first resonator is used in one of these partial modes. It will in fact be recalled that the two modes of the same partial are separated by a relative frequency difference of the order of 10%.
In an improved embodiment, the oscillator comprises a third piezoelectric resonator having in common with the first resonator a mode at said resonance frequency, whose quality factor is of the same order of size as that of the second resonator, said third resonator being connected in series between the ungrounded terminal of the first resonator and the base of the transistor.
The oscillator is advantageously associated with a temperature detector and a servocontrol of the temperature of the first resonator.
In a variant, the oscillator comprises a Varicap diode connected in series with said third resonator so as to form a frequency control for the oscillator, it comprises a temperature detector and a compensation circuit producing a control voltage on the Varicap diode so that the frequency drift of the oscillator is compensated for. The first resonator may advantageously have, at said resonance frequency, a stable frequency mode depending on the temperature as well as a so called thermometric mode whose frequency varies with the temperature, the temperature detector then being formed by an oscillator operating in the thermometric mode of the first resonator and whose frequency varies therefore with the temperature thereof. The first resonator can for example be an SC cut quartz, the stable frequency mode being a C mode, and the thermometric mode a B mode. The C mode and the B mode may both belong to the fundamental F or both to a partial of the same rank.
In a preferred embodiment, the temperature sensitive oscillator employs a second transistor. A fourth piezoelectric resonator is connected between the ungrounded end of the first resonator and the base of the second transistor. A capacitive divider bridge having a so called middle point is connected between the base of the second transistor and ground, with the emitter of the second transistor being loaded by a second load resistor. A fifth piezoelectric resonator connects the second middle point to the emitter of the second transistor. The fourth and fifth resonators having in common a mode at the frequency of said thermometric mode of the first resonator, with a quality factor between 30 and a 1000 times smaller than the latter. The collector of the second transistor thereby produces a frequency voltage which varies substantially linearly with the temperature of the first resonator.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood from reading the following description given by way of non limitative example with reference to the drawings which show:
FIG. 1, one embodiment of an oscillator according to the invention;
FIG. 2 an embodiment of a temperature compensated oscillator according to the invention; and
FIG. 3, curves representative of the temperature frequency drift in the case of an SC cut quartz.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, a transistor T1 is supplied with the voltage +V at its collector C1, a divider bridge R1,R2 biasing its base B1. The emitter E1 is loaded by a load resistor R3. The piezoelectric resonator Q1 is connected between the base B1 of transistor T1 and ground. A capacitive divider bridge C1,C2 having a so called middle point P1 is also connected between the base B1 of transistor T1 and ground. A piezoelectric resonator Q2 is connected between the middle point P1 and the emitter E1 of transistor T1. The function of this resonator Q2 is to form a band-pass filter at the operating frequency of the oscillator. Thus, resonator Q2 must have a mode at the same frequency as the mode of resonator Q1 chosen for determining a frequency of the oscillator. According to the invention, the band-pass filter is formed by choosing resonator Q2 with a quality factor which is 30 to 1000 times smaller than that of resonator Q1. Thus, it is certain that the oscillator will start up at the chosen frequency without being troubled by thermodrifting. It is very easy to provide a resonator with a quality factor smaller than that of resonator Q1, since several parameters influence the quality factor of the resonator. Such parameters comprise for example the quality of the cut and the thickness and arrangement of the electrodes. In fact, thick electrodes at the position where the resonator vibrates cause a very considerable drop in the quality factor. In practice, it is high quality resonators which have high quality factors and are therefore very expensive. On the other hand, resonators having lower or much lower quality factors are easier to form and are less expensive. It is in any case possible to provide a resonator having a given quality factor. For example, with a resonator Q1 made from quartz may be associated a resonator Q2 made from lithium tantalate.
In FIG. 2, an oscillator such as shown in FIG. 1, is associated with a second oscillator having a high thermal drift. If we refer in fact to FIG. 3, an SC cut quartz has for its partial 3 a C mode whose frequency drift curve as a function of the temperature has a small slope close to a temperature θ° and a practically linear B mode over a large temperature range with high thermal drift. According to the invention, the C mode of the partial 3 of quartz Q1 is used as temperature stable frequency reference and the slight thermal drift of this C mode is compensated for by using the B mode of the same quartz as temperature sensor. This design has the very important advantage of using, as temperature sensor, the quartz itself whose frequency it is desired to stabilize. It is then certain that the temperature measured is exactly that which is desired.
In so far as the oscillator part in the C mode is concerned, the same elements as those in FIG. 1 are shown with the same references. This oscillator has however in addition a frequency control circuit comprising a low value Varicap diode CR connected between two capacitors C5 and C6 in series with the base of transistor T1. A biasing resistor R5 biases the cathode of the varicap diode CR and a control voltage VC is applied to the anode of the varicap diode CR through a coupling resistor R6. Such a frequency control circuit for slightly varying the frequency of the oscillator is moreover known per se. In addition, in the base circuit of transistor T1 is connected a piezoelectric resonator Q3 having a mode at the frequency of the C mode of resonator Q1 corresponding to the desired frequency of the oscillator, with a quality factor of the order of 30 to 1000 times smaller and preferably 30 to 100 times smaller. Resonator Q.sub. 3 improves the separation between the C modes at which the main oscillator operates and the B mode at which the oscillator used as thermal sensor operates.
The thermal sensor oscillator has a CLAPP circuit similar to that of the oscillator of FIG. 1. The collector of a transistor T2 is biased by a voltage B through a biasing resistor R9 and its base by a divider bridge R8, R4. Furthermore, a capacitive divider bridge C3, C4 having a so called middle point P2 is connected between the base B2 of transistor T2 and ground. The emitter E2 of transistor T2 is loaded by a load resistor R10. The piezoelectric resonator is connected between the emitter E2 and the middle point P2. It has a mode whose frequency is that of the B mode close to the C mode at which the main oscillator operates. The same goes for a resonator Q4 connected between the base B2 and the ungrounded electrode of resonator Q1. Resonators Q4 and Q5 have a quality factor 30 to 1000 times smaller and preferably a 100 times smaller than that of the B mode considered for resonator Q1. The output voltage ST present at the collector C2 of transistor T2 is fed to a frequency-voltage converter 1 which outputs a digitalized voltage which is fed into a memory 2. Each value of the output voltage of converter 1 corresponds to an address in memory 2, at which address a stored voltage is read at a rate determined by a sampling clock H. This stored voltage is the reflection of the correspondance between the thermal drift curves in the B mode and the C mode of the quartz Q1 and its value corresponds to that of the voltage VC which must be fed into the frequency variation circuit of the main oscillator for providing the thermal drift correction. For this, each value read in the memory at the rate of the sampling clock is fed to a digital-analog converter 3 whose output voltage VC is applied to the resistor R6.

Claims (7)

What is claimed is:
1. A piezoelectric oscillator of the Clapp type operating in the overtone mode comprising:
a first piezoelectric resonator having a resonance frequency at which the oscillator is to operate, said first resonator being connected between the base of a transistor and ground, as well as a capacitive divider bridge connected between the base of said transistor and ground having a middle point and the emitter of the transistor being loaded by a load resistor;
a second piezoelectric resonator having in common with the first piezoelectric resonator a mode at said resonance frequency, but whose intrinsic quality factor is between 30 and 1000 times smaller than that of the first piezoelectric resonator, said second piezoelectric resonator being connected between said middle point of the capacitive divider bridge and the emitter of said transistor; and
a third piezoelectric resonator having in common with the first resonator a mode at said resonance frequency, but whose quality factor is of the same order of size as that of said second resonator, said third resonator being disposed in series between the ungrounded terminal of said first resonator and the base of said transistor.
2. The oscillator as claimed in claim 1, comprising a temperature detector and a temperature responsive control means for controlling the first resonator.
3. The oscillator as claimed in claim 1, wherein a Varicap diode is disposed in series with said third resonator so as to form a frequency control for said oscillator, comprising a temperature detector as well as a compensation circuit introducing a control voltage on said Varicap diode so that the frequency drift of the oscillator is compensated for.
4. The oscillator as claimed in claim 2, wherein said first resonator has, at said resonance frequency, a stable frequency mode depending on the temperature as well as a so called thermometric mode whose frequency varies with the temperature and wherein said temperature detector is formed by an oscillator operating in the thermometric mode of said first resonator and whose frequency thus varies as a function of the temperature thereof.
5. The oscillator as claimed in claim 4, wherein said first resonator is an SC cut quartz and said stable frequency mode is a C mode and the thermometric mode is a B mode.
6. The oscillator as claimed in claim 5, wherein said C mode and said B mode both belong to the fundamental F or to a partial of the same rank.
7. The oscillator as claimed in claim 4, wherein said temperature sensitive oscillator comprises a second transistor, a fourth piezoelectric resonator connected between the ungrounded end of the first resonator and the base of said second transistor, a second capacitive divider bridge having a second middle point and being connected between the base of said second transistor and ground, the emitter of said second transistor being loaded by a second load resistor and a fifth piezoelectric resonator connecting the second middle point to the emitter of said second transistor, the fourth and fifth resonators having in common a mode at the frequency of said thermometric mode of said first resonator, but with a quality factor between 30 and 1000 times less than this latter, the collector of said second transistor thus producing a voltage of a frequency varying substantially linearly with the temperature of said first resonator.
US06/715,822 1984-03-27 1985-03-25 Piezoelectric oscillator with crystal filter and temperature compensation Expired - Fee Related US4616194A (en)

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FR8404746 1984-03-27
FR8404746A FR2562349B1 (en) 1984-03-27 1984-03-27 PIEZOELECTRIC OSCILLATOR OPERATING IN APERIODIC MODE

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JP (1) JPS60220605A (en)
DE (1) DE3563502D1 (en)
FR (1) FR2562349B1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4851790A (en) * 1988-04-11 1989-07-25 Westinghouse Electric Corp. Crystal controlled oscillator exhibiting reduced levels of crystal-induced low frequency noise, vibration sensitivity and circuit temperature rise
US5517053A (en) * 1995-01-09 1996-05-14 Northrop Grumman Corporation Self stabilizing heater controlled oscillating transistor
US20090308142A1 (en) * 2006-09-29 2009-12-17 Naoki Onishi Sensing instrument
US20150280686A1 (en) * 2012-10-08 2015-10-01 Rakon Limited Multi-Function Frequency Control Device
TWI548204B (en) * 2010-03-29 2016-09-01 Kyocera Kinseki Corp Piezoelectric vibrator

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2270223B (en) * 1992-08-29 1996-06-19 Motorola Israel Ltd A communications system
JP2007049254A (en) * 2005-08-08 2007-02-22 Nippon Dempa Kogyo Co Ltd Crystal oscillator
JP4892267B2 (en) * 2006-03-31 2012-03-07 日本電波工業株式会社 Dual mode crystal oscillation circuit
JP2008177800A (en) * 2007-01-18 2008-07-31 Nec Corp Oscillator

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3372348A (en) * 1966-05-02 1968-03-05 Motorola Inc Oscillator having piezoelectric elements operating at different harmonic modes
FR2501435A1 (en) * 1981-03-03 1982-09-10 Cepe Stable and spectrally pure Clapp oscillator with quartz crystal - has two series reactances connected to transistor emitter and higher value supplementary reactance between common point and base
US4484157A (en) * 1981-03-03 1984-11-20 Compagnie D'electronique Et De Piezo-Electricite Voltage controlled crystal oscillator having wide frequency range

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3372348A (en) * 1966-05-02 1968-03-05 Motorola Inc Oscillator having piezoelectric elements operating at different harmonic modes
FR2501435A1 (en) * 1981-03-03 1982-09-10 Cepe Stable and spectrally pure Clapp oscillator with quartz crystal - has two series reactances connected to transistor emitter and higher value supplementary reactance between common point and base
US4484157A (en) * 1981-03-03 1984-11-20 Compagnie D'electronique Et De Piezo-Electricite Voltage controlled crystal oscillator having wide frequency range

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4851790A (en) * 1988-04-11 1989-07-25 Westinghouse Electric Corp. Crystal controlled oscillator exhibiting reduced levels of crystal-induced low frequency noise, vibration sensitivity and circuit temperature rise
US5517053A (en) * 1995-01-09 1996-05-14 Northrop Grumman Corporation Self stabilizing heater controlled oscillating transistor
US20090308142A1 (en) * 2006-09-29 2009-12-17 Naoki Onishi Sensing instrument
US8051714B2 (en) * 2006-09-29 2011-11-08 Nihon Dempa Kogyo Co., Ltd. Sensing instrument
TWI548204B (en) * 2010-03-29 2016-09-01 Kyocera Kinseki Corp Piezoelectric vibrator
US20150280686A1 (en) * 2012-10-08 2015-10-01 Rakon Limited Multi-Function Frequency Control Device
US10116282B2 (en) * 2012-10-08 2018-10-30 Rakon Limited Multi-function frequency control device
US11309863B2 (en) 2012-10-08 2022-04-19 Rakon Limited Multi-function frequency control device

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JPS60220605A (en) 1985-11-05
DE3563502D1 (en) 1988-07-28
EP0157697A1 (en) 1985-10-09
FR2562349B1 (en) 1986-06-27
FR2562349A1 (en) 1985-10-04
EP0157697B1 (en) 1988-06-22

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